It is proposed to continue ongoing studies designed to elucidate the efficacy of strategies for weight loss and long-term weight maintenance in moderately overweight men and women, and to investigate the influence of maintained loss of body fat on major risk factors for coronary heart disease. In a new randomized, controlled trial, 90 overweight men and 90 overweight premenopausal women (relative weight 120-160%; age 30-40) will be recruited and randomly assigned in equal proportions either to weight loss by a combination of moderate caloric restriction and progressive endurance exercise; or to a no-weight loss control group, for the first year. Participants will be healthy but sedentary, non-smokers, and (for women) not pregnant or on oral contraceptives. At baseline and at the end of one year, after a period of weight stabilization, measurements will be made of body weight and composition, nutrient intake, basal metabolic rate, plasma concentration of lipids, lipoproteins and apolipoproteins, and resting and ambulatory blood pressure. During the second year of the trial, regular exercise will be firmly incorporated into the lifestyle of the weight-reduced participants, and caloric intake will no longer be manipulated or regulated by the investigators. Measurements at the end of the second year, in a "lifestyle steady state," will examine the long-term effects in initially overweight men and women of an evolution to the chronically active, non-obese state, on body composition, basal metabolic rate, caloric intake, plasma lipoproteins and blood pressure. Follow-up studies are also proposed in about 100 overweight, non-smoking men aged 30-59 who have already successfully lost substantial body fat in the Stanford Weight Control Project by one-year supervised programs of either caloric restriction alone (n=50) or increased physical activity alone (n=50). A six-month program of behavioral maintenance will be provided, followed by measurements of body composition and cardiovascular risk factors at one-year post-weight loss. Ascertainment of body weight only is also proposed at 2, 3 and 4 years post-weight loss, to assess long-term weight maintenance attained by intensive instruction in dieting or in exercising.